1. Field of the Invention
The present invention relates to a separation and recycling method, in particular to a separation and recycling method for recycling uranium and fluoride from a waste liquid sequentially and separately.
2. Description of the Related Art
A waste liquid containing uranium and fluoride is generally produced in refineries for refining uranium mines, or laboratories of research centers, and these waste liquids are classified as radwaste liquors which are strictly controlled to protect ecological environments. In a traditional way of processing the waste liquid containing uranium and fluoride, a calcium salt (Ca2+) is added to perform a chemical precipitate, such that the uranium will be coprecipitated in calcium fluoride (CaF2) and cause a solid waste disposal or reuse issue. If a uranium-containing solid is buried in the same way as a radwaste, there will be a concern of a fluoride eroding a container, and the reuse of calcium fluoride is restricted by many related laws and regulations on uranium-containing matters. Thus, the reusability of the waste liquid is very low. Therefore, it is an important subject to avoid the coprecipitation of uranium and fluoride, but recycle uranium and fluoride from a waste liquid.
Traditional methods of recycling uranium and fluoride as disclosed in U.S. Pat. No. 4,256,702 and an article entitled “Recovery of uranium filtrate of ammonium diuranate prepared from uranium hexafluoride” and published by J. A. Seneda, et al in the Journal of Alloys and Compounds in 2001 can achieve the effect of removing uranium or fluoride. However, if these methods are applied to a waste liquid containing uranium and fluoride, then the coprecipitation will occur, and the methods cannot meet the requirement of removing uranium and fluoride separately. Another method as disclosed in U.S. Pat. No. 4,769,180 provides a way of removing fluoride and uranium separately by adding a magnesium (Mg) compound and sulfuric acid to neutralize a waste liquor, form a precipitate and then distill the formed precipitate in order to separate fluorine and uranium. However, this method requires distillation, and hydrofluoric acid (HF) will be produced in the distillation process. Hydrofluoric acid is an extremely strong corrosive agent having a very strong erosion capacity on silicon and silicon dioxide, thereby being able to corrode glass. In addition, hydrofluoric acid is highly poisonous and can be absorbed through a skin membrane, respiratory tract and gastrointestinal tract.